Studies of Dirhodium Tetra(trifluoroacetate). 3. Solid State Isomers of the Compound Rh2(O2CCF3)4(THF) Prepared by Sublimation

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Abstract
The monoadduct of dirhodium tetra(trifluoroacetate) with THF has been obtained by deposition from the vapor phase. The compound Rh2(O2CCF3)4(THF) crystallizes in two isomeric forms, 1 and 2, whose structures have been determined by X-ray crystallography. The crystallographic parameters are as follows: for 1, triclinic space group P1̄ with a = 9.557(2) Å, b = 10.126(2) Å, c = 11.840(4) Å, α = 95.97(2)°, β = 90.40(2)°, γ = 115.58(1)°, and Z = 2; for 2, triclinic space group P1̄ with a = 8.6347(3) Å, b = 9.678(1) Å, c = 13.773(4) Å, α = 73.182(5)°, β = 74.622(5)°, γ = 89.76(1)°, and Z = 2. Compound 1 is unique as the only extended structure where dirhodium carboxylate molecules are bridged by a single exogenous atom. The oxygen atom of the THF ligand coordinates to the axial positions of two Rh2 units so that a one-dimensional zigzag chain is formed. The bridging is slightly asymmetric with Rh−O(THF) distances of 2.363(6) and 2.407(6) Å, and the Rh−O(THF)−Rh angle is 111.8(3)°. The crystal structure of 2 is not polymeric. Pairs of Rh2(O2CCF3)4(THF) units are associated through O atoms of carboxylate groups to produce a dimer of dimers. The lengths of the terminal Rh−O(THF) and axial bridging Rh···O(Ac) interactions are 2.214(7) and 2.406(6) Å, respectively.

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